That's the problem with words vs collections of letters when it comes to ultra-short domains.
"url" means, well, URL (if you'll forgive the tautology) so it has a relatively clear use. But because of URL, fewer companies may be interested in "url" as a 3-letter acronym divorced from its existing meaning.
"lfp" on the other hand has no meaning at all (it's a random example so I may have boobed and picked something with an obscure meaning I don't know) - that means it is useful, and only useful, as a 3-letter acronym.
That may well make it a more attractive prospect than a different 3 letters that already have a clear primary meaning.